Jargon Buster - D

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Process that is used to remove limescale (calcium carbonate) from heat exchanger waterways.


A device using differential pressures to operate or function . Common applications in a boiler are the diverter valve and air pressure switch.

Digital Programmer

A digital programmer has an electronic display, but does the same job as the time clock. It may have separate controls for the heating and hot water.

Double radiators

A radiator with two heating panels.

Drain the system

Term used when water from a central heating system is to be purposefully emptied.


A device to drain a system.

Ducted warm-air system (AGS)

A system using ducting to distribute the heating air.


Enclosure designed to accommodate water pipes and fittings, electrical cables and other services.


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